You like the guy, and you would like to kiss him, but you want to keep it a secret from your (many) mutual friends. Aren't you setting yourself up for a lot of pain?

Why don't you take responsibility for for your actions and feelings? There's nothing wrong about them, and if you feel confident, people will mostly not care about it. On the other hand, if you are ashamed and secretive about your behavior, you will evoke mistrust and suspicion from those around you. People might actually misunderstand and be disappointed in you ("she does not trust me, so she kept me in the dark about it, I'm probably not as close a friend of her as I thought", and all that kind of crap). Besides, these things nearly always filter out, so being sneaky about it ends up catching up with you.

But more importantly, you are being unfair and dishonest to the guy. Why should he bear the weight of your insecurities? He has nothing to be ashamed of, so why should he behave in a fishy and hypocritical manner? Also, don't tell him to "go with the flow" if in reality you are not at all ready for that. Say it if you really mean it. Loosen up, you're doing something entirely normal, be bold and confident, just as you should. I could understand if you wished to avoid kissing because you don't feel ready for that on a personal level. But if it's because you are worried about "what others might think", I think you are doing it backwards, and will probably have a harder time having a nice and rewarding relationship.